bufio: add Writer.AvailableBuffer #47527
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This proposal has been added to the active column of the proposals project |
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This seems reasonable. Does anyone object to this? |
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Based on the discussion above, this proposal seems like a likely accept. |
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No change in consensus, so accepted. 🎉 |
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Change https://golang.org/cl/345569 mentions this issue: |
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This adds a new Writer.AvailableBuffer method that returns an empty buffer with a possibly non-empty capacity for use with append-like APIs. The typical usage pattern is something like: b := bw.AvailableBuffer() b = appendValue(b, v) bw.Write(b) It allows logic combining append-like APIs with bufio.Writer to avoid needing to allocate and manage buffers themselves and allows the append-like APIs to directly write into the buffer for a bufio.Writer. Fixes golang#47527 Change-Id: I9cd169f3f8e8c7cd40818caf3daf1944c826fc66 Reviewed-on: https://go-review.googlesource.com/c/go/+/345569 Trust: Joe Tsai <joetsai@digital-static.net> Run-TryBot: Joe Tsai <joetsai@digital-static.net> TryBot-Result: Go Bot <gobot@golang.org> Reviewed-by: Ian Lance Taylor <iant@golang.org> (cherry picked from golang.org/cl/345569)
dsnet
added a commit
to tailscale/go
that referenced
this issue
Jan 19, 2022
This adds a new Writer.AvailableBuffer method that returns an empty buffer with a possibly non-empty capacity for use with append-like APIs. The typical usage pattern is something like: b := bw.AvailableBuffer() b = appendValue(b, v) bw.Write(b) It allows logic combining append-like APIs with bufio.Writer to avoid needing to allocate and manage buffers themselves and allows the append-like APIs to directly write into the buffer for a bufio.Writer. Fixes golang#47527 Change-Id: I9cd169f3f8e8c7cd40818caf3daf1944c826fc66 Reviewed-on: https://go-review.googlesource.com/c/go/+/345569 Trust: Joe Tsai <joetsai@digital-static.net> Run-TryBot: Joe Tsai <joetsai@digital-static.net> TryBot-Result: Go Bot <gobot@golang.org> Reviewed-by: Ian Lance Taylor <iant@golang.org> (cherry picked from golang.org/cl/345569)
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There are many APIs in Go that append to a
[]byteand return a[]byte.Unfortunately, these APIs operate poorly with
bufio.Writersince that type only accepts[]byteas an input (via theWritemethod) and never provides a[]byte. This requires logic trying to combine append-like functionality withbufio.Writerto be responsible for allocating a buffer, whenbufio.Writeralready has a buffer.I propose the addition of a new method that provides access to the underlying
[]byte:Example usage:
In the common cases where
bw.Available()is large enough,strconv.AppendUintappends to the buffer without allocating. When the buffer is passed toWrite, the underlying call tocopyreturns immediately without actually copying since the source and destination are identical. This saves us both an allocation and a copy.In the rare case where it allocates, the subsequent
Writecall still works as expected, but needs to copy.The detriment of this API is that it exposes the internal buffer of
bufio.Writerwhen it was previously impossible to access it. However, the other types in the package (i.e.,ReaderandScanner) already provide unsafe access to the underlying buffer via theReader.Peek,Reader.ReadSlice, andScanner.Bytesmethods.The text was updated successfully, but these errors were encountered: